Variable resistor



J u ne 22 ,1926.

C.- HARDY VARIABLE RESISTOR Filed Dec. 23. 1924 lNVEN'I-OR Charles HardgA'IT NEYS" Patented June 22, 1926.

UNITED STAKES 1,590,163 PATENT OFFICE.

CHARLES HARDY, OF NEW YORK, N. Y., ASSIGNOR '1'0 AMSCO PRODUCTS INC., OFNEW YORK, N. Y., A CORPORATION OF NEW YORK.

VARIABLE RESISTOR.

Application filed December 23, 1824. Serial No. 757,874.

This invention relates to electrical resistance units, and has specialreference-to the provision of variable resistors or resistance devices.

A prime desideratum of my present invention relates to the productionvofvariable resistors or resistance devices especially des gned for usein controlling electron discharge tube andother circuits in radioreceiving sets. As is well known, one of the methods of controlling thevolume, tone and other operating characteristics of a radio receivingset is by regulating the filament current to control the electronemission of the electron discharge tubes, this bein accomplished by theadjustment of a variable resistor placed in the filament or tubecircuit.

The type of variable resistor commonly employed for this use comprises astator which includes a resistance element such as a wire Wound unit anda pair of connectors 0r bindin osts, one of which is electricallyconnecte to the resistance element, and a rotor which includes anoperating shaft anda contact blade fixed thereto, which contact blade ismovable over the resistance element. In this type of construction, tworegions must be relied upon for establishing electrical connectionbetween the rotor and stator parts, one being the point of en agement between the movable blade and tie resistance element, and the other beingthe oint of connection bet-ween the operating is aft and the secondbinding post; and for the eflicient operation of the tube circuit andthe radio receiving set, it is necessary to establish or make eflicientand continuous electrical connections at both regions. In prior oonstructions of these variable resistors, the contact blade, which is made of aresilient material,

is usually relied upon to bring the statorand rotor' parts at bothregions into the desired electrical engagement. It is found, however,that the contact blade can not be made strong enough to. efi'ectivel'perform its intended functions and that the. connection between theshaft and second binding po'stis interfered with by dust or other foreign matter settling between the parts, and i as a consequence,vsuch'electrical engagement as is obtained in these resis'torsisinsuflicient to avoid microphonic noises in the telephones due to thepresence. of microphonic contacts between'the stator and rotor partsduring adjustment. A principal object of the present invention residesin the provision of an improved variable resistor in which electricalcontact between the rotor and stator parts at all points or regionsthereof is effectively established, with the construction such that allmicrophonic noises in the receiver are eliminated during adjustmentcontrol of the filament circuit, such adjustment being obtainablesmoothly and with a high degree of precision.

Other and further prime objects of the invention include the provisionof a variable resistor in which the electrical engagement between thestator and 'rotor" parts at the different regions, thereof is obtainedby resilient elements acting in opposition, each assisting the other inproducing the desired electrical contact between ad acent stator androtor parts; the further provision of a variable resistor of the naturereferred to in which the parts which are depended upon for producing theelectrical engagement are, wherever feasible, efl'ectively housed orsealed against the entry of foreign matter so that the same are alwaysmaintained in clean condition and good operating service; and the stillfurther provision of a variable resistor in which the parts arerelatively coordinated to permit not only the rapid. assembly of theparts into a salable unit, but quick and efiicient assembly of the partsof the resistor properly coordinated on a" panel or like support.

To the accomplishment of the foregoing and such other objects as willhereinafter appear, my invention consists in the elements and theirrelation one to the other, as hereinafter particularly described andsought to be defined in the claims; reference being had to theaccompanying drawings, which vention, and in which:

Fig. 1 is a cross-sectional view of the variable resistor of myinvention showing the same mounted on a panel or like support.

Fig. 2 is a view taken in cross-section in the plane of line 2-2, F ig.Iii and j Fig. 3 is a perspective view of the parts of the resistor indetached formation. 1 10.

Referring now more in detail to thedrawings, the improved resistor of myinvention comprises a stator unit a constructed for attachment to apanel orlike sup ort, and a rotor r rotatably mounted in t e stator.

.show the preferred embodiment of my in- Y a wire of suitable resistanceabout a flexible insulating core 10", the said resis- 'tance unit beingbent into curved or arcuate form and clamped by a flexible clampingelement 11 in an arcuate-shaped channel 12 W provided in a. supportingbase 13, which? 1 supporting base is preferably made of an insulatingmaterial such as amolded phenol condensation product. The stator furtherincludes the usual pair of binding posts 14 w and 15 serving asconnectors for the circuit conductors, the binding post 15 being con-'nected to one terminal or lead of-the resistance coil 10, and thebinding post 14 being connected in a manner to be described presm entlyto other parts ofi the stator unit.

'As heretofore stated; a principal object of the present inventioncenters about the provision of a variable resistor in which electricalcontact between the rotor and 5 stator parts at relatively movablepoints or regions thereof is effectively established, with theconstruction such that all microphonic noises in the radio receivingsystem of which the resistorfiforms a part are eiiectively eliminatedduring adjustment control' of the filament circuit. To contribute towards this desired end, the stator of my invention: comprises an elementwhich may be described as a connector element, the same functioning as aconnecting means between a rotor part and the binding post 14. Thisconnector comprises in the preferred construction' a tubular shapedelement 16 fixedly attached to the insulating base 13, the saidconnector element having an irregular, such as a square orhexagonal-shaped head 16 seated in a correspondingly shaped centraldepression inthe insulating base 13, the said 1 connector elementbeing-externally threaded v as at 16" for receiving a clamping nut 17and a panel mounting nut 18. Y 'The connector element 16 is electricallyi connected to the binding post 14 by means of the metallic strip 19,one end of. which is joined to the binding post 14, and the otherend-ofjw'hich is clamped between the clamping .nut 17 and a central bossportion '13 of the insulating base. These parts of the --stator defineor comprise a unit which. is

mountable on asupport such as a'panel 7) I by means of the panelmounting nut 18,

' which as' shown in Fig. 1 of the drawings.

is threaded-1y received by the outer end'of the connector element 16.Preferably, as

shown in the drawings, the face of the clamping nut 17 adjacent to thepanel mounting nut :18 is made flush with the-'rim 13 of the insulatingbase, so that the parts 5 may be securely fastened to the panel byscrewing the panel mounting nut 18 on the LRWOJBE threaded end of theconnector without straining the insulating base. If desired, theinsulating base may also beprovided with a bore 20 for receivingadditional means, for securing the stator to the panel.

The rotor of my invention comprises an operating shaft 21 mounted forrotation in the connector element 16, and, a resilient contact blade 22which is fixed to said shaft in a manner to be described resently, andwhich is arranged to be mova le in engagement with a wall of theresistance element 10, as clearly shown in the drawings. in I thepreferred construction as exemplified in the drawings, the operatingshaft 21 is threaded at one end, as at 21*; and the movable contactblade 22 is fixed to a threaded nut 23 which is received by the threadedend 21 of the operating shaft and is locked thereto by means of a locknut 24;, suitable washers 25 and 26 being interposed between the locknut 24 and an annular lip 23 which is integral with the nut 23 and whichclamps the blade 22 in fixed position on the nut.

By means of this construction, the contact blade 22 isfsecurelyconnected both mechanically and electrically to theoperating shaft 21,and this construction, as will be shown presently, assists in permittingthe obtaining of the desired operation of the rotor and the electricalconnection between the same and the connector 16. v For producing thedesired electrical contact or connection between the connector 16 andthe binding post operating shaft 21, I provide a spring 27 arrangedtoefi'ect electrical connection between the shaft and the connectorelement,.the said spring being correlated or associated with theresistor parts so as to act in opposition to the reother in producingthe desired electrical engagement between contiguous rotor andstator-parts.

Thespr1ng'27 to this end preferably comprises a compression spring, thesaid spring being arranged in the tubular-shaped connector 16 andencircling the shank of-the operating shaft 21, the ends of the springbearing axially in opposite directions on shouldered portions of theoperating shaft;

and connector element respectively, as clear- 1y shown in Fig. 1 of thedrawlngs. As will be apparent, this spring is active on the shaft 21 ina direction which is transmitted to the resilient contact blade 22toassist'in same and the resistance element 10, and" conversely, thecontact blade 22 is re-active on the shaft 21 in adirection to' move themaking good electrical contact between the d shaft against the spring 27so-as to secure good electrical engagement between both endsof-thespring 27 'with the-shaft 21 and connector 16. Thus at both regions ofconnection between the rotor and the stator, effective electricalcontact is established. It will also be noted that the tubular connectorelement 16 is constructed to serve as a bushing or bearing ofsubstantial length for the operatin shaft, and that the said connectordesira ly serves as a protective housing and complete enclosure for thespring 27 so that the same may be sealed against the entry offoreignmatter and the spring maintained in clean condition and in goodoperating service.

The manner of making and assembling the improved resistor of myinvention and the many advantages thereof will be fully apparent fromthe above detailed description thereof. It will be apparent that the,parts of the resistor unit may be readily assembled for purposes ofseparate sale; and when it is desired to attach the resistor to a panel,the same may be rapidly disassembled and connected to the panel by thepurchaser or user without altering the pre-v determined cooperationbetween the parts. Thus the stator unit 8 will firstbe attached to thepanel p by screwing the panel mounting nut 18 onto the threaded end ofthe connector element 16, which end is inserted through a bore providedin the panel. After thus securing or clamping the stator units rigidlyin position on the panel, the operating shaft 21, after receiving thespring 27, is inserted through the connector element 16, the end of theshaft 21 being thereafter threaded into the nut 23 of the contact blade22. the limit of this threading action being determined by a portion 21provided in the shaft 21, which shoulder portion abuts the outer face ofthe panel mounting nut 18. In threading the shaft 21 onto the nut 23,however, a slight amount of axial play is provided for so as to minimizeany bin ing action between the parts and 'so as to permit the spring andcontact blade to I act in opposition to each other. The nut 23 is thensecurely locked in position on the operating shaft by means of the locknut 24.

The operating shaft 21 is provided with a finger grip or control handle28 which is secured thereto by means of the screw. 29. The-parts maythus be assembled in a facile manner on the panel, with thepredetermined arrangement of the stator and rotor parts properlycoordinated.

While I have shown and described my invention in the preferred form, itwill be apparent that many modifications and changes may be made in thestructure disclosed without departing from the spirit of the invention,defined in the following claims.

' I claim:

, 1. A variable resistor comprising a stator member including asupporting base,, a re.-

shoulder sistance element mounted thereon and a connector element fixedthereto, a rotor member including an operating shaft rotatable but heldagainst axial movement in said base and a movable resilient contactblade fixed to said shaft and movable over said resistance element, anda spring located between and arranged to bear axially in oppositedirections on said shaft and said connector element, the resilientcontact blade and the spring being correlated to act in opposition, eachfunctioning to assist the other in producing efficient electricalengagement between a rotor art and a stator part.

2. A variable resistor comprising a stator member including a supportingbase, a re-' sistance element mounted thereon and a tu bular shapedconnector element fixed thereto, a rotor member including an operatingshaft rotatable in said connector element and (a movable contact bladefixed to said' shaft and -movable over said resistance element, and aspring located between and arranged to bear axially in oppositedirections on said shaft and said connector element, the said tubularconnector element forming a bushing for the shaft and a housing for thespring.

3. A variable resistor comprising a stator member including a supportingbase, a resistance element mounted thereon, a connector element fixedthereto and a pair of binding posts connected respectively to the.connector and resistance elements, a rotor member including anoperating shaft rota-table but held against axial movement in said baseand a movable resilient contact blade fixed to saidshaft and movableover said resistance element, and a spring located between and arrangedto bear axially in 'opposite directions on said shaft and said connectorelement, the resilient contact blade and the spring being correlated toact in opposition. each functioning to assist the other in producingefiicient electrical engagement between a rotor part and a stator part.

4. A variable resistor comprising a. stator member including asupporting base, a. re.- sistance element mounted thereon, atubularshaped connector element fixed thereto, and a pair of binding postsconnected respectively to th'e'connectorand resistance elements, a rotormember including an operating shaft rotatable in said connector elementspring beingcorrelated to act in opposition,

each functioning to assist the other in producing efiicient electricalengagement between adjacent rotor and stator parts, the said tubularconnector element forming a bushing for the shaft and a housing for thesaid spring.

5. A variable resistor comprising a stator member including a supportingbase, a resistance element mounted thereon and a connector element fixedthereto, a rotor member including an operating shaft threadedat one endrotatable in said base and a resilient contact blade having a threadednut received by and locked to said shaft, said blade being movable oversaid resistance element, and a spring arranged between said shaft andsaid connector elementand active axially on said shaft, the contactblade and the spring being correlated to act in opposition.

6. A variable resistor comprising a stator member including asupportingbase, a resistance element mounted thereon, a threadedconnector element fixed thereto, and a panel mountinglock nut threadedlyreceivable by said connector element, a rotor member including anoperating shaft rotatable in said base and a movable contact blade fixedto said shaft and movable over said resistance element, and a springarranged between said, shaft and said connector element and activeaxially on said shaft.

7. A variable resistor comprising a stator member including a supportingbase, a resistance element mounted thereon, and a tubular-shapedconnector element fixed thereto, a rotor member including an operatingshaft, threaded at one end, rotatable in said connector element and amovable contact blade having a threaded nut received by and locked tosaid shaft, said 'blade being movable over said resistance element, anda spring electrically connecting said shaft and said connector element,the contact blade and the spring being correlated to act in opposition,each functioning to assist the other in producing efiicient electricalengagement be-v tween adjacent rotor and stator parts.

8. A variable-resistor comprising a stator member including a supportingbase, a resistance element mounted thereon, a threaded tubular-shapedconnector element fixed thereto, and a panel'mounting nut threadedlyattached to said connector element, a rotor member including anoperating shaft threaded at one end,-rotatable in said connector,element and a resilient movable contact blade having a threaded nutreceived by and locked to said shaft, said blade being movable over saidresistance element, and a spring electrically connecting said shaft andsaid connector element, the contact blade and the spring beingcorrelated to act in op ed tubular-shaped connector fixed thereto and apanel mounting nut threadedly attached to said connector element, arotor member including an operating shaft, threaded at one end,rotatable in said connector element and a resilient contact blade havinga threaded nut received by and locked to said shaft, said blade beingmovable over said resistance element, and a compression spring locatedbetween and ar ranged to bear axially in opposite directions on saidshaft and said connector element, the said tubular connector elementforming a bushing for the shaft and a housing for the spring, theresilient contact blade and the spring being correlated to act inopposition, each functioning to assist the other in producing efiicientelectrical engagement between adjacent rotor and stator parts.

10. A variable resistor comprising a stator member including aninsulating supporting base, a wire wound arcuate-shaped resistanceelement mounted thereon, a threaded tubular-shaped connector fixedthereto, binding posts connected respectively to said resistance andconnector elements, and a panel mounting nut threadedly attachedto saidconnector element, a rotor member including an operating shaft, threadedat one end, r0- tatable. in said connector'element and a resilientcontact blade having a threaded nut received by and locked to saidshaft, said blade being movable over said resistance element, and acompression spring located between and arranged to bear axially in'opposite directions on said shaft and said connector element, the saidtubular connector element forming a bushing for the shaft and a housingfor the spring, the resillent contact blade and the spring beingcorrelatedto act in opposition, each functioning to ass st theother inproducing efliclent electrical en-- 'gagement'between adjacent rotor andstator

